The main use for spouses as a male character is to increase your influence in their family, gain legitimacy should you ever decide to contest the throne yourself and to throw feasts at your castle/town.
Troop order determines the order that your units will spawn, the ones at the top spawn first, the ones on the bottom last. If you're unable to take all your troops into battle at once it's important, if your party size is small or you've used the
Battle Size Changer to increase the size of battles over the default it's only really useful for determining the starting positions (left to right).
As for battle tactics, the simplest go to tactic is to place your archers on a hill, your infantry in front of them and your cavalry to the side ready to charge into the flank. However different tactics work better on different factions/armies so it's best to experiment till you find methods that work the best for your playstyle/opponents. Personally I prefer to place my archers to the side of my infantry, if you do it right the enemy will still focus on your infantry but your archers will have a clear line of fire into their flank.